All about Teaching and Learning English as a Second Language

Menu

Tag Archives: Speech defects due to brain disorders

In 1861, the French surgeon, Pierre Paul Broca, described his patients who had lost the ability to speak after injury to the posterior inferior frontal gyrus of the brain. Since that time, an infinite number of clinical and functional imaging studies have relied on this brain^behaviour relationship as their anchor for the localization of speech functions. Clinical studies of Broca’s aphasia often assume that the deficits in these patients are due entirely to dysfunction in Broca’s area, thereby attributing all aspects of the disorder to this one brain region.
Moreover, functional imaging studies often rely on activation in Broca’s area as verification that tasks have successfully tapped speech centres. Despite these strong assumptions, the range of locations ascribed to Broca’s area varies broadly across studies.

Here are two mental case studies that proves Speech functions can be damaged whenever Broca brain part, or Broca’s Aphasia is affected. Take the first case study named PETER.

Location of Damage: Corpus Callosum :

Peter began to suffer from complex partial seizures at the age of 8. His seizures were severe, despite taking antiepileptic medication; so, at the age of 20, after struggling with his condition for over 12 years, he and his doctors agreed to have him undergo a commissurotomy.

The commissurotomy involved a surgical incision of Peter’s corpus callosum. The corpus callosum is the major cerebral nerve tract that connects the brain’s right and left cerebral hemispheres together; and therefore, serves as the major communication pathway for intrahemispheric signals. Removal or damage to one’s corpus callosum would result in impaired communication between the two sides of the brain.

On one hand, Peter’s surgery was a success, as it did end up attenuating the magnitude of his seizures. On the other hand, however, Peter was left much different than before. For example, he was not able to respond with the left side of his body to verbal input. If asked to “Stand like a Boxer,” his left side would sag and appear lackluster, while his right side would behave appropriately.

Because his brain had, literally, been split into two separate pieces, his left and right sides were often behaving like two separate people.

He complained that his left hand would turn off television shows that he was enjoying,

that his left leg would not always walk in the intended direction, and

that his left arm would occasionally begin to fight with the right side of his body.

It is clear from Peter’s case that the brain works best when it is capable of functioning as a single, cohesive unit,
as opposed to multiple ones.

Brains’ Lateralization:

The left and right brains are connected by an intricate network of nerve fibres called the corpus callosum. It was the ancient Egyptians who first noticed that the left brain tends to control the right side of the body and the right brain tends to control the left side of the body. Although each hemisphere is almost identical in terms of structure, each hemisphere operates in an entirely different way and are associated with very different activities. This is known as specialization or lateralization.

LEFT HEMISPHERE
The left brain is the logical brain responsible for words, logic, numbers, analysis, lists, linearity and sequence. It controls the right side of your body.RIGHT HEMISPHERE
The right brain is the creative brain and is responsible for rhythm, spatial awareness, colour, imagination, daydreaming, holistic awareness and dimension. It controls the left side of your body.CORPUS CALLOSUM
The corpus callosum is a thick band of nerve fibres which connect the brain cells in one hemisphere to those in the other hemisphere. The two hemispheres keep up a continuous conversation via this neural bridge.

Case study No 2: N.I. The Woman Who Read With Her Right Hemisphere

Location of Damage: Complete Removal of Left Hemisphere

Before contracting her illness, N.I. was a perfectly normal girl. Unfortunately, at the age of 13, she began to experience convulsions, along with deteriorated speech and motor abilities. CT scans revealed ischemic (lack of blood flow) brain damage to her left hemisphere. N.I. was still experiencing symptoms two years after the onset of her illness, and her right limbs had become paralyzed. In an attempt to relieve these symptoms, a total left hemispherectomy (removal of a hemisphere in the brain) was performed.

Following this procedure, her seizures subsided completely. Sadly, however, her surgery had taken away her ability to read correctly. (Most people, including N.I., use their left hemispheres for language related tasks)Post surgery, N.I. was able to recognize letters, but was totally incapable of translating them into sounds. She could read concrete familiar words (ie: fan), but could not pronounce even simple nonsense words (ie: neg). Her reading errors indicate that she reads on the basis of meaning and appearance of words rather than by translating the individual letters into sounds. For instance, when shown the word “fruit” she would respond by saying: “juice.”

Her responses are similar to people with a disorder known as ‘deep dyslexia’, which is an inability to apply rules of pronunciation while reading. Deep dyslexics can still pronounce familiar words based on their specific memories of them, but similar to N.I., they cannot pronounce nonsensical words, or words they are unfamiliar with